It is a commonplace situation for a pump intake to be placed in a body of water such as a river, lake, or an estuary. Generally it is placed to one side of any major stream flow in a relatively quiescent region. In this invention, such a region is for convenience described as a "bay". In fact, a screen according to this invention may and often will be at least a part of the boundary of the bay.
Bodies of water with which this invention is concerned are likely to have a considerable burden of material such as leaves, branches and vines. In addition, and of Great importance to this invention, fish often swim in them, and unless care is taken they will be drawn into the pump.
Laws protective of such fish, especially of smaller wild fish--salmon for example, provide very serious penalties for the discovery of even one of these fish in an inlet bay, or at the downstream side of the pump. The penalties can include very substantial monetary fines, and even worse, an injunction against withdrawing water from the body of water.
Intake pumps for irrigation systems commonly have screens to exclude fish and detritus, but the rate of flow of water adjacent to the intake port of the pump is such as to draw the solid material against the screen and quite possibly clog it. Screens have in fact been provided close to intake ports, but because they are located at the region of rapid water flow to the pump, lesser screen aperture sizes used to exclude solids can compromise the rate of flow to the pump.
It is an object of this invention to provide a screen which comprises a part of the boundary of a bay in which the intake port of a pump is disposed. This screen is provided with apertures that are suitably sized to exclude fish of "penalty" size. Because such apertures are likely to be clogged by detritus, the screen is provided with self-cleaning means which have the dual function of clearing the apertures and of discouraging fish from attempting to swim through the screen apertures.